alpha: Add string-fza, string-fzb.h, string-fzi.h, and string-shift.h

While alpha has the more important string functions in assembly,
there are still a few for find the generic routines are used.

Use the CMPBGE insn, via the builtin, for testing of zeros.  Use a
simplified expansion of __builtin_ctz when the insn isn't available.

Checked on alpha-linux-gnu.

Co-authored-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>
Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>

4 files changed, 218 insertions, 0 deletions

diff --git a/sysdeps/alpha/string-fza.h b/sysdeps/alpha/string-fza.h
new file mode 100644
index 0000000..b72ce82
--- /dev/null
+++ b/sysdeps/alpha/string-fza.h
@@ -0,0 +1,60 @@
+/* Basic zero byte detection.  Generic C version.
+   Copyright (C) 2023 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <http://www.gnu.org/licenses/>.  */
+
+#ifndef _STRING_FZA_H
+#define _STRING_FZA_H 1
+
+#include <string-misc.h>
+#include <string-optype.h>
+
+/* The CMPBGE instruction creates a bit mask rather than a byte mask.
+   However, if we narrow find_t to either 'int' or 'uint8_t', we get
+   unnecessary truncation instructions from the 'unsigned long' type
+   returned by __builtin_alpha_cmpbge.  */
+typedef op_t find_t;
+
+static __always_inline find_t
+find_zero_all (op_t x)
+{
+  return __builtin_alpha_cmpbge (0, x);
+}
+
+static __always_inline find_t
+find_eq_all (op_t x1, op_t x2)
+{
+  return find_zero_all (x1 ^ x2);
+}
+
+static __always_inline find_t
+find_zero_eq_all (op_t x1, op_t x2)
+{
+  return find_zero_all (x1) | find_zero_all (x1 ^ x2);
+}
+
+static __always_inline find_t
+find_zero_ne_all (op_t x1, op_t x2)
+{
+  return find_zero_all (x1) | (find_zero_all (x1 ^ x2) ^ 0xff);
+}
+
+/* Define the "inexact" versions in terms of the exact versions.  */
+#define find_zero_low		find_zero_all
+#define find_eq_low		find_eq_all
+#define find_zero_eq_low	find_zero_eq_all
+
+#endif /* _STRING_FZA_H */
diff --git a/sysdeps/alpha/string-fzb.h b/sysdeps/alpha/string-fzb.h
new file mode 100644
index 0000000..e3934ba
--- /dev/null
+++ b/sysdeps/alpha/string-fzb.h
@@ -0,0 +1,52 @@
+/* Zero byte detection; boolean.  Alpha version.
+   Copyright (C) 2023 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <http://www.gnu.org/licenses/>.  */
+
+#ifndef _STRING_FZB_H
+#define _STRING_FZB_H 1
+
+#include <sys/cdefs.h>
+#include <string-optype.h>
+
+/* Note that since CMPBGE creates a bit mask rather than a byte mask,
+   we cannot simply provide a target-specific string-fza.h.  */
+
+/* Determine if any byte within X is zero.  This is a pure boolean test.  */
+
+static __always_inline _Bool
+has_zero (op_t x)
+{
+  return __builtin_alpha_cmpbge (0, x) != 0;
+}
+
+/* Likewise, but for byte equality between X1 and X2.  */
+
+static __always_inline _Bool
+has_eq (op_t x1, op_t x2)
+{
+  return has_zero (x1 ^ x2);
+}
+
+/* Likewise, but for zeros in X1 and equal bytes between X1 and X2.  */
+
+static __always_inline _Bool
+has_zero_eq (op_t x1, op_t x2)
+{
+  return has_zero (x1) | has_eq (x1, x2);
+}
+
+#endif /* _STRING_FZB_H */
diff --git a/sysdeps/alpha/string-fzi.h b/sysdeps/alpha/string-fzi.h
new file mode 100644
index 0000000..aba7ca4
--- /dev/null
+++ b/sysdeps/alpha/string-fzi.h
@@ -0,0 +1,62 @@
+/* string-fzi.h -- zero byte detection; indices.  Alpha version.
+   Copyright (C) 2023 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <http://www.gnu.org/licenses/>.  */
+
+#ifndef _STRING_FZI_H
+#define _STRING_FZI_H
+
+#include <stdint.h>
+#include <string-optype.h>
+#include <string-fza.h>
+
+/* Note that since CMPBGE creates a bit mask rather than a byte mask,
+   we cannot simply provide a target-specific string-fza.h.  */
+
+/* A subroutine for the index_zero functions.  Given a bitmask C,
+   return the index of the first bit set in memory order.  */
+static __always_inline unsigned int
+index_first (find_t c)
+{
+#ifdef __alpha_cix__
+  return __builtin_ctzl (c);
+#else
+  c = c & -c;
+  return (c & 0xf0 ? 4 : 0) + (c & 0xcc ? 2 : 0) + (c & 0xaa ? 1 : 0);
+#endif
+}
+
+/* Similarly, but return the (memory order) index of the last bit
+   that is non-zero.  Note that only the least 8 bits may be nonzero.  */
+
+static __always_inline unsigned int
+index_last (find_t x)
+{
+#ifdef __alpha_cix__
+  return __builtin_clzl (x) ^ 63;
+#else
+  unsigned r = 0;
+  if (x & 0xf0)
+    r += 4;
+  if (x & (0xc << r))
+    r += 2;
+  if (x & (0x2 << r))
+    r += 1;
+  return r;
+#endif
+}
+
+#endif /* _STRING_FZI_H */
diff --git a/sysdeps/alpha/string-shift.h b/sysdeps/alpha/string-shift.h
new file mode 100644
index 0000000..4e2cb2f
--- /dev/null
+++ b/sysdeps/alpha/string-shift.h
@@ -0,0 +1,44 @@
+/* Shift unaligned word read.  Alpha version.
+   Copyright (C) 2023 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <http://www.gnu.org/licenses/>.  */
+
+#ifndef _STRING_SHIFT_H
+#define _STRING_SHIFT_H 1
+
+#include <limits.h>
+#include <stdint.h>
+#include <string-fza.h>
+
+/* Return the mask WORD shifted based on S_INT address value, to ignore
+   values not presented in the aligned word read.  */
+static __always_inline find_t
+shift_find (find_t word, uintptr_t s)
+{
+  return word >> (s % sizeof (op_t));
+}
+
+/* Mask off the bits defined the the S alignment value.  */
+static __always_inline find_t
+shift_find_last (find_t word, uintptr_t s)
+{
+  s = s % sizeof (op_t);
+  if (s == 0)
+    return word;
+  return word & ~((op_t)-1 << s);
+}
+
+#endif /* _STRING_SHIFT_H */